This invention relates generally to traps for removal of condensate from a steam/condensate mixture in a steam system for return to a boiler, and more specifically to a steam restricter device which may be retrofitted to existing steam trap structure.
Presently, there are many closed steam systems, for instance steam heating systems, which relay upon steam traps designed around the turn of the century for removal of condensate from the steam. These steam traps are inefficient and have moving parts making them subject to frequent failure, which causes substantial losses of steam and increases costs for maintenance and replacement of these devices. One type of steam trap with moving parts commonly used on steam heat radiators is a bellows steam trap including a bowl shaped trap into which steam is fed and from which condensate is discharged through an opening in the bottom of the trap to the boiler. The bellows is made of heat expansible material and suspended from a cover on the top of the trap. The bellows expands to plug the opening to prevent the escape of steam when the trap is full of steam and thus at a relatively high temperature. The bellows contracts when the trap temperature falls (corresponding to the presence of significant amounts of condensate), allowing condensate to escape through the opening to the condensate return.
More efficient and reliable systems have been developed which employ a constricted orifice design exploiting the properties of two-phase flow in saturated steam. More specifically, an orifice is placed at the inlet to the condensate return line which is sized according to the particular operating characteristics (e.g., pressure and temperature) of the system so that condensate will flow through the orifice, but at such a rate and volume so as to substantially block the orifice to the flow of steam, thus restraining the steam in the system. Reference is made to U.S. Pat. No. 4,171,209 (Brown) which shows a such a steam trap employing the principles of the constricted orifice. Greater efficiencies in the removal of condensate with minimal steam loss have been achieved through the employment of modified Venturi nozzles, such as is shown in U.S. Pat. No. 4,171,209.
However, the existence of efficient, reliable orifice-type steam restricter devices for removing condensate is of little consolation to owners of older steam systems having old style steam traps who are faced with significant capital expenditures in order to remove the old steam traps and replace them with the new traps. Moreover, such constricted orifice devices have required frequent cleaning to avoid clogging from debris in the system. Thus, there is presently a need for an inexpensive, relatively steam restricter device which may be easily retrofitted to existing steam trap structure, and easily maintained thereafter.